Holder for sharpening edged tools



'Nov. 19, 1968 A. J. TIDWELL 3,411,249

HOLDER FOR SHARPENING EDGED TOOLS Filed April 15, 1966 m vew r00. ARLAND.1. rmwzu.

- A I rorney United States Patent Oifice 3,411,249 HOLDER FOR SHARPENINGEDGED TOOLS Arland J. Tidwell, 1185 North 50 East, Orem, Utah 84057Filed Apr. 13, 1966, Ser. No. 542,253 2 Claims. (Cl. 51-219) ABSTRACT OFTHE DISCLOSURE Apparatus for holding a drill bit while it is beingsharpened on a grinding wheel. The apparatus includes a plate with agroove in its top surface in which the drill bit is clamped. A fingerextends from the underside of the plate toward the grinding Wheel andcooperates with the underside of the plate to envelop the outer edge ofthe tool rest on the grinder. Using this finger, the apparatus ispivoted on the outer edge of the tool rest in such a manner as to guidethe point of drill bit over the grinding wheel to sharpen the cuttingedge and give the drill bit point its desired rake angle.

This invention relates to a holder for drill bits that maintains thedrill bit in proper alignment relative to the surface of a grindingwheel, while the point of the bit is being ground.

In the past, holders for grinding drill bits have been complex andawkward to use. They have usually comprised a complicated apparatus thatis both expensive in its initial cost and requires valuable labor timeto set it up before it can be used to grind drill bits.

The object of my invention is to provide a simple, inexpensive devicefor holding a drill bit while it is being sharpened on a bench grinder.My invention is designed to enable the operator to obtain a properlyground drill point with a minimum amount of elfort during both theset-up and the grinding operations.

In its present preferred form, my holder comprises a flat plate with agroove in its top surface, and a simple clamp means for holding thedrill bit within this groove. A finger extends from the bottom surfaceof the plate and is bent towards one end of the plate. While the pointof the drill bit is being ground, the plate is rotated up and down,using the tool rest of the bench grinder as a fulcrum. The tool rest isinserted in a pocket formed by the bent finger and the bottom surface ofthe plate.

The embodiment of my holder disclosed herein is also easily adjustablefor use in grinding other tools, such as cold chisels, lathe tools,plane irons, and rotary mower spokeshaves. The use of my holder forthese purposes is shown and described in my co-pending United Statesapplication, Ser. No. 516,921, filed Dec. 28, 1965, now abandoned.

A complete understanding of the invention may be obtained from thefollowing detailed description and the attached drawings, in which:

FIGURE 1 is a plan view of my holder showing a drill bit clampedthereon;

FIGURE 2 is a side view of the holder of FIGURE 1;

FIGURE 3 is a side view of the holder and drill bit of FIGURE 1 in useon a conventional bench grinder; and

FIGURE 4 is a front end view of the point of a drill bit, illustratingthe surfaces that are being ground during the use of my holder.

The drill bit holder 2, shown from the top in FIGURE 1, comprises anelongated flat base plate 4 and an adjustable clamping head 6 that issecured to the plate 4 by a wing bolt 8. V-groove 10 in the top surfaceof the plate 4 extends diagonally across the plate and beneath the freeend of the clamping head 6.

As may be seen in FIGURE 2, this free end of the Patented Nov. 19, 1968clamping head 6 is spaced from the top surface of the plate 4 and hastwo wing bolts 12 which are threaded into the head 6. The wing bolts 12extend downwardly onto the top of a drill bit D that rests in the groove10. The drill bit D is held stationary in the groove 10 by tighteningthe wing bolts 12. The drill bit D is positioned in the groove 10 sothat its point P extends beyond the end of plate 4 and into contact withthe stone S of grinder G, which is shown in its entirety in FIGURE 3.

The point of the drill bit is actually a pair of surfaces on the frontend of the bit, as illustrated by the point P in FIGURE 4. One edge ofeach surface of the point P is a cutting lip L, and the cutting lips Ldo the main cutting of the hole as the drill is advanced through theworkpiece. In grinding each surface of the point P, the lip L should beparallel with the grinding surface of the stone S. To obtain thiscondition, the V-groove 10 housing the drill bit D is positioned at anangle with the grinding surface of the stone S that is complementary tothe point angle N of the drill bit (FIGURE 1).

As shown in FIGURE 2, a finger 14 extends downwardly from the bottomsurface of the plate 4 and toward the same end of the plate beyond whichthe point of the drill bit extends. The finger 14 has a concave surface16 facing the bottom surface of plate 4. The surface 16 and the bottomsurface of the plate 4 form a pocket 18 that is adapted to engageslidably the outer edge of tool rest R of bench grinder G, as shown inFIGURE 3.

The finger 14 and pocket 18 extend transversely across the underside ofplate 4. Finger 14 is positioned so that the lines along which the sidesof the pocket 18 engage the tool rest R are parallel to one cutting lipof point P on drill bit D. Thus, in the manufacture of the holder 2, theangle between the V-groove 1t and the line 19 at the base of pocket 18is made complementary to the point angle of the drill bit.

In the use of the drill bit holder 2, the bit D is placed in theV-groove 10 as shown in FIGURES 1 and 2. The holder is then placed nextto the stone S of grinder G, with the outer edge tool rest R in slidingengagement with the sides of the pocket 18. With the holder 2 heldapproximately in the solid line position shown in FIGURE 3, the drillbit D is then moved forward in the V-groove 10 until its point Pcontacts the grinding stone S. The wing bolts 12 are then tightenedagainst the bit D to hold it stationary in the groove 10, and thegrinder G is turned The point P is ground by rotating the holder 2 backand forth between the solid-line and dotted-line positions of the holder2, as indicated by arrows X in FIGURE 3. The outer end of the tool restR acts as a sliding fulcrum during this rotation, with the concavesurface 16 of the finger 14 and the bottom surface of plate 4 sliding inopposite directions over the upper and lower corners of the rest R. As aresult of this movement of the holder 2, the point P of the bit D isgiven short, back-and-forth, grinding strokes against the grinding stoneS.

This grinding is repeated on the other surface of point P, and as aresult, the cutting lips L (FIGURE 4) are sharpened. In addition, themotion of the drill bit D, caused by the back-and-forth rotation ofholder 2 on rest R, grinds the point P to its proper rake angle.

The rake angle of the drill point P is the angle by which the surface ofthe point slopes away from the cutting lip and thus departs from a tubeconical surface. The rake angle of the drill point is very critical,since a too-small rake angle will cause too much friction between thedrill point and the bottom of the hole that is being cut, and a rakeangle that is too large will impose too great a stress on the part ofthe drill bit around the cutting lip. Either of these conditions canseverely damage the drill bit. Thus,

3 it is a significant advantage that the drill bit holder I havedisclosed is simple in construction, yet enables the operator grindingthe drill point to obtain a proper rake angle with a minimum of effort.

The holder 2 may be used without the clamping member 6, if the operatordesires to hold the bit D in the groove 10 with his hand. However, theoperator must be careful to hold the bit firmly while grinding, or elsethe force of the grinding stone against the bit will cause the bit tofly oiT the holder 2, and possibly injure someone.

The holder 2 is also capable of being adjusted for use in grinding othertools. By loosening the wing bolt 8, the clamping head 6 may be rotatedabout the bolt 8 to a number of different positions for holding varioustypes of tools. Marks 20 and 21 (FIGURE 1) are provided on the clampinghead 6 and are designed to be matched with various marks on the plate 4.When the marks 20 and 21 are matched with marks (I on plate 4, asillustrated in FIGURE 1, the clamping head 6 is in a proper position forholding the drill bit D. Matching the mark 20 with mark a puts the rearof head 6 in proper position for holding cold chisels. Similarly,matching mark 20 with mark b positions the head 6 for holding planeirons, lathe tools, or wood chisels, and matching mark 20 with mark cpositions the head 6 for holding rotary lawn mower spokeshaves. Scribedguide lines 22 are provided on the rear of plate 4 to aid in properlyorientating these tools with respect to the grinding surface of thegrinding stone S.

Ribs 23 are provided on the bottom side of plate 4 in back of finger 14.These ribs extend transversely across the plate 4, and when a tool otherthan a drill bit is being ground, the holder 2 is placed on the toolrest R with the outer edge of the rest housed in the dihedral angle 24between the ribs 23. The manipulation of the holder 2 when held on thetool rest R in this position is shown and described in my co-pending US.Patent application, Ser. No. 516,921, filed Dec. 28, 1965.

While one embodiment of my invention has been shown and describedherein, other modifications will be readily apparent that are within thescope of the appended claims.

I claim:

1. Apparatus for grinding the point and sharpening the cutting lip of adrill bit on a grinding stone equipped with a tool rest, said apparatuscomprising an elongated plate, means on one side of said plate forholding a drill bit with its point extending beyond an end of saidplate, and a finger extending from the other side of said plate andgradually curving toward said end of the plate beyond which the point ofsaid drill bit extends, said finger having an arcuate concave surfacefacing said other side of said plate, said finger and said other side ofthe plate enveloping and slidably engaging the outer edge of said toolrest so as to stroke against said grinding stone the point of a drillbit held by said holding means and grind said point to a desired rakeangle, and said finger having a width extending transversely across saidplate such that said pivoting of said finger and said other side of saidplate about said tool rest has a rotational axis parallel to the cuttinglip of said drill bit when held by said bit holding means.

2. Apparatus of claim 1 in which said plate has a groove in one side ofsaid plate, the walls of said groove forming a part of said means forholding said drill bit, said apparatus also including a clamp membermounted on said plate for securing said drill bit in a fixed position insaid groove.

References Cited UNITED STATES PATENTS 1,155,213 9/ 1915 Clark 5 l-2201,275,208 8/ 1918 Bockshe 51-220 2,612,012 9/1952 Becker 51-2191,944,540 1/1934 Bailey 512l9 3,121,983 2/ 1964 English 51-219 HAROLD D.WHITEHEAD, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,411,249 November 19 1968 Arland J. Tidwell It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 2, line 65, "tube" should read true Signed and sealed this 10thday of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR.

